1. Field
This invention comprises a rapidly installed wastewater treatment plant solids and liquids recovery system apparatus and method employing chemical dewatering and biological treatment technology particularly suited for the treatment of saline wastewaters.
2. State of the Art
Various sewage treatment methods and plants are known. Most large municipal systems employ a series of settling ponds sequentially concentrating the solids contained in wastewater either with or without polymers for separation from liquids via mechanical separation means, such as belt presses. To produce a clean effluent that can be safely discharged to watercourses, wastewater treatment operations use three or four distinct stages of treatment to remove harmful contaminants; according to the United Nations Environmental Programme Division of Technology, Industry, and Economics Newsletter and Technical Publications Freshwater Management Series No. 1, “Bio-solids Management: An Environmentally Sound Approach for Managing Sewage Treatment Plant Sludge” stating: “Each of these stages mimics and accelerates processes that occur in nature.
Preliminary wastewater treatment usually involves gravity sedimentation of screened wastewater to remove settled solids. Half of the solids suspended in wastewater are removed through primary treatment. The residual material from this process is a concentrated suspension called primary sludge, subsequently undergoing additional treatment to become bio-solids.
Secondary wastewater treatment is accomplished through a biological process, removing biodegradable material. This treatment process uses microorganisms to consume dissolved and suspended organic matter, producing carbon dioxide and other by-products. The organic matter benefits by providing nutrients needed to sustain the communities of microorganisms. As microorganisms feed, their density increases and they settle to the bottom of processing tanks, separated from the clarified water as a concentrated suspension called secondary sludge, biological sludge, waste activated sludge, or trickling filter humus.
One unfortunate byproduct of conventional preliminary and secondary wastewater treatment is significant evaporation of the liquid phase of the treated effluent resulting in a significant increase in its brine content.
Tertiary or advanced treatment is used when extremely high-quality effluent is required, including direct discharge to a drinking water source. The solid residual collected through tertiary treatment consists mainly of chemicals added to clean the final effluent, which are reclaimed before discharge, and therefore not incorporated into bio-solids. Tertiary or advanced treatment does not reduce the treated wastewater brine content, requiring energy intensive Quaternary brine treatment removal using reverse osmosis and distillation, and other methods.
Combined primary and secondary solids comprise the majority of material used at municipal plants for bio-solids production. Careful management throughout the entire treatment process allows plant operators to control the solids content, nutrient value and other constituents of bio-solids.